Stefan Maria Kuczyński, pen name Włodzimierz Bart (21 September 1904 – 30 March 1985), was a Polish historian and academic specializing in the medieval history of the Kingdom of Poland during the Piast dynasty and the Jagiellon dynasty, especially in the period of King Władysław II Jagiełło.
Kuczyński also served as editor-in-chief of illustrated monthly Śląsk in 1946–1948, published in Jelenia Góra, and the scientific journal Nauka i Sztuka, one of the first of its kind in postwar Poland.
Kuczyński studied philology, law and history in the Second Polish Republic at the University of Warsaw, and received a doctorate in 1932 for his work Rządy litewskie na Siewierszczyźnie w II połowie XIV wieku, under the direction of Oskar Halecki.
He worked first as high-school teacher in Warsaw and later as lecturer at his own alma mater since 1937 (until the invasion of Poland), with the title of docent at the Institute of Medieval History.
During the occupation of Poland he took part in clandestine Tajne komplety.